In a wireless cellular network, such as those which comply with standards such 3rd Generation Partnership Project (3GPP), 3rd Generation Partnership Project 2 (3GPP2), Universal Mobile Telephone Service (UMTS) or Wideband CDMA (WCDMA), Long Term Evolution (LTE), etc., a wireless communication device (WCD) (also referred to as a mobile station (MS), mobile unit (MU), subscriber station, user equipment (UE)) communicates with a fixed base station (BS) that is coupled to a wired core network. The BS has a particular coverage area or range that defines a cell site or “cell” in the cellular network. When the WCD is located within a cell site defined by a particular BS, the WCD can communicate over a wireless link with the BS. The WCD can move geographically, and when the WCD moves out of range of the BS, it may connect or “handover” to a new BS and starts communicating through the new BS.
Physical and Logical Channels for WCD and BS Communication
Each cell site utilizes a number of physical radio channels for communications between the BS and the WCD(s) within communication range of that BS. Uplink channels are used by a WCD to communicate information to the BS, whereas downlink channels are used by a BS to communicate information to WCDs. The bandwidth of the uplink channel and downlink channel is fixed. The uplink bandwidth is divided into a number of physical radio channels that are each a portion of the available uplink bandwidth capacity. Each physical radio channel can support a number of logical channels. These logical channels are used to carry out defined “functions” within a physical channel. In general, logical channels can be used to carry either (1) traffic/data information, or (2) control/signaling information. The BS dynamically controls usage of these logical channels by a particular WCD or particular groups of WCDs. Each channel be classified as being either common (i.e., shared by all WCDs) or dedicated (i.e., for use by a particular WCD or group of WCDs). Traffic channels are dedicated meaning that they are reserved for use by a particular WCD or group of WCDs. Control channels can be either common or dedicated. Common control channels provide control information for more than one WCDs and are thus “shared” resources, whereas dedicated control channels provide control information for one WCD.
Random Access Channel (RACH) Resources
One common or shared control channel is the uplink Random Access Channel (RACH). One or more RACHs can be implemented in a portion of the uplink bandwidth; the number of RACHs is semi-static meaning that a certain number of RACHs are allocated and this number does not change dynamically based on changes in loading within the cell that is defined by the base station. These RACHs are used by WCDs to transmit a relatively small amount of data to the BS. For example, the RACH can be used by a WCD to gain initial access to the cellular network (e.g., for call origination, registration messages, and paging response). It can be used by the WCD to get the attention of a BS in order to initially synchronize its transmission with the BS and gain access to the network. The WCD can also use a RACH to request services or dedicated uplink/downlink resources (or bandwidth) from the BS. The RACH can also be used for short data bursts (e.g., non-real-time dedicated control or traffic data, for example, sending Short Messaging Service (SMS) packets). For instance, when operating idle mode, the WCD continuously monitors a control channel from the BS to determine if there is an incoming call for that WCD. In particular, when a call is sent to the WCD, the BS sends a page message to the WCD on the control channel, and the WCD responds by sending a message on a RACH to let the network know which particular cell the WCD is currently in. By contrast, when the WCD attempts to initiate a call, the WCD sends a request message to the BS on a RACH to let the network know which particular cell the WCD is currently in. The WCD can also transmit messages over the RACH to negotiate reservation of a dedicated resources (traffic channels and control/signaling channels) with the BS. Once negotiated, the WCD can then use these resources in a communication session with the BS.
Because the RACH is a shared resource, messages transmitted on the RACH are not scheduled (in contrast to messages transmitted on a dedicated channel that is assigned exclusively to one WCD at a time). At the same time, as noted above, the number of uplink RACHs in each cell site is normally semi-static and is fixed based on the average distributed load on specific cells, anticipated average system capacity, etc. As such, when the traffic load within a cell increases (e.g., the number of users in a specific cell increases or the activity of existing users in a specific cell increases) well beyond its average load, many users will be attempting to use the same fixed amount of uplink RACHs. When two or more subscribers simultaneously attempt to use the same uplink RACH this can result in collisions. For example, it has recently been proposed that a portion of the 700 megahertz cellular spectrum will allocated for public safety use during deployment of public safety networks, for example, at an incident scene. In these type of networks, the traffic load in cells that are near the incident scene increases greatly as an incident escalates, and then following the incident returns to more normal or average levels. It is critical that public safety workers have access to the network during the incident and not competing with other users for RACHs needed to establish a communication session.
Thus, in some situations, it may be desirable to restrict usage of particular uplink RACHs to particular set of WCDs.
Static Subscriber Classes
In some cellular networks, such as those that comply with 3GPP and 3GPP2 standards, subscribers can be statically classified into groups or classes. One way to prevent a particular subscriber/WCD from using certain uplink RACH is by: (1) grouping subscribers into general “static” classes (e.g., permitted access class or restricted access class), (2) advertising information from the BS that specifies whether WCDs belonging to particular classes are allowed (or not allowed) to use particular uplink RACHs in its cell, and (3) blocking particular subscriber WCDs from using particular uplink RACHs if they belongs to the restricted access class. However, one problem with this “one-dimensional” static classification approach (i.e., grouping subscribers into either a permitted or a restricted access class) is that some subscribers are allowed to use all applications, while others are not allowed to use any applications regardless of the application type. In other words, it is an “all-or none” approach. It would also be desirable to allow more users to be authorized to use certain basic services or perform certain applications, while still restricting their access to other services or applications.
Moreover, the rejection of a request during the first access attempt (e.g., by blocking the subscriber on the application level) will likely cause the subscriber WCD to retry and make additional access attempts using the uplink RACH. Therefore the total amount of access attempts using the uplink RACH is likely to increase, and this can potentially create a bottleneck condition on the uplink RACH and increase blocking probability with respect to other subscriber WCDs that are also attempting to use the uplink RACH.
In addition, in certain situations it is undesirable to statically allocate uplink RACHs to particular classes of subscribers. Static allocation of uplink RACHs could result in too few or too many uplink RACHs being allocated for use by public safety subscribers since the peak cell load is not statically distributed and varies greatly throughout the course of an incident.
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The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.